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Encyclopedia > Brown dwarf
This brown dwarf (smaller object) orbits the star Gliese 229, which is located in the constellation Lepus about 19 light years from Earth. The brown dwarf, called Gliese 229B, is about 20 to 50 times the mass of Jupiter.
This brown dwarf (smaller object) orbits the star Gliese 229, which is located in the constellation Lepus about 19 light years from Earth. The brown dwarf, called Gliese 229B, is about 20 to 50 times the mass of Jupiter.

Brown dwarfs are sub-stellar objects with a mass below that necessary to maintain hydrogen-burning nuclear fusion reactions in their cores, as do stars on the main sequence, but which have fully convective surfaces and interiors, with no chemical differentiation by depth. Brown dwarfs occupy the mass range between that of large gas giant planets and the lowest mass stars; this upper limit is between 75[1] and 80 Jupiter masses (MJ). Currently there is some question as to what separates a brown dwarf from a giant planet at very low brown dwarf masses (~13 MJ ), and whether brown dwarfs are required to have experienced fusion at some point in their history. In any event, brown dwarfs heavier than 13 MJ do fuse deuterium and those above ~65 MJ also fuse lithium. The only planet known to orbit a brown dwarf star is 2M1207b. Image File history File links Brown_Dwarf_Gliese_229B.jpg Description This brown dwarf (smaller object) orbits the star Gliese 229, which is located in the constellation Lepus about 19 light years from Earth. ... Image File history File links Brown_Dwarf_Gliese_229B.jpg Description This brown dwarf (smaller object) orbits the star Gliese 229, which is located in the constellation Lepus about 19 light years from Earth. ... Image of Gliese 229 A and B. Gliese 229 (also written as Gl 229 or GJ 229) is a cool, red dwarf star about 19 light years away in the constellation Lepus. ... Lepus (IPA: , Latin: ) is a constellation, lying just south of the Celestial equator, below the constellation Orion, and possibly representing a hare being chased by Orion the hunter. ... STAR is an acronym for: Organizations Society of Ticket Agents and Retailers], the self-regulatory body for the entertainment ticket industry in the UK. Society for Telescopy, Astronomy, and Radio, a non-profit New Jersey astronomy club. ... General Name, Symbol, Number hydrogen, H, 1 Chemical series nonmetals Group, Period, Block 1, 1, s Appearance colorless Atomic mass 1. ... The deuterium-tritium (D-T) fusion reaction is considered the most promising for producing fusion power. ... Hertzsprung-Russell diagram The main sequence of the Hertzsprung-Russell diagram is the curve where the majority of stars are located in this diagram. ... This article does not cite any references or sources. ... The eight planets and three dwarf planets of the Solar System. ... Adjectives: Jovian Atmosphere [4] Surface pressure: 20–200 kPa[9] (cloud layer) Scale height: 27 km Composition: Jupiter (IPA: or ) is the fifth planet from the Sun and the largest planet within the solar system. ... Deuterium, also called heavy hydrogen, is a stable isotope of hydrogen with a natural abundance in the oceans of Earth of approximately one atom in 6500 of hydrogen (~154 PPM). ... General Name, Symbol, Number lithium, Li, 3 Chemical series alkali metals Group, Period, Block 1, 2, s Appearance silvery white/grey Standard atomic weight 6. ... 2M1207b is an extrasolar planet orbiting the brown dwarf 2M1207, a star in the constellation Hydra approximately 200 light years from Earth. ...

Contents

History

Brown dwarfs, a term coined by Jill Tarter in 1975, were originally called black dwarfs, a classification for dark substellar objects floating freely in space which were too low in mass to sustain stable hydrogen fusion (the term black dwarf currently refers to a white dwarf that has cooled down so that it no longer emits heat or light). Alternative names have been proposed, including Planetar and Substar. Jill Cornell Tarter (born 1944) is an American astronomer and the current director of the Center for SETI Research. ... Year 1975 (MCMLXXV) was a common year starting on Wednesday (link will display full calendar) of the Gregorian calendar. ... A black dwarf is a hypothetical astronomical object: a white dwarf so old that it has cooled down so that it no longer emits significant heat or light. ... This article or section does not adequately cite its references or sources. ... Planetars are used in astronomy to represent one of two concepts: Planetars are brown dwarfs which formed through accretion or core collapse within a circumstellar disc, forming like a planet does. ... Substar, an unofficial name sometimes applied to Brown dwarf stars, sub-stellar objects with a mass below that necessary to maintain hydrogen-burning nuclear fusion reactions in their cores. ...


Early theories concerning the nature of the lowest mass stars and the hydrogen burning limit suggested that objects with a mass less than 0.07 solar masses for Population I objects or objects with a mass less than 0.09 solar masses for Population II objects would never go through normal stellar evolution and would become a completely degenerate star (Kumar 1963). The role of deuterium-burning down to 0.012 solar masses and the impact of dust formation in the cool outer atmospheres of brown dwarfs was understood by the late eighties. They would however be hard to find in the sky, as they would emit almost no light. Their strongest emissions would be in the infrared (IR) spectrum, and ground-based IR detectors were too imprecise for a few decades after that to firmly identify any brown dwarfs. Stars can be grouped into two general types called Population I and Population II. The criteria for classification include space velocity, location in the galaxy, age, chemical composition, and differences in distribution on the Hertzsprung-Russell diagram. ... It has been suggested that this article or section be merged into Compact star. ... Deuterium, also called heavy hydrogen, is a stable isotope of hydrogen with a natural abundance in the oceans of Earth of approximately one atom in 6500 of hydrogen (~154 PPM). ... In astronomy, the solar mass is a unit of mass used to express the mass of stars and larger objects such as galaxies. ... View of Jupiters active atmosphere, including the Great Red Spot. ... Image of two girls in mid-infrared (thermal) light (false-color) Infrared (IR) radiation is electromagnetic radiation of a wavelength longer than that of visible light, but shorter than that of radio waves. ...


Since those earlier times, numerous searches involving various methods have been conducted to find these objects. Some of those methods included multi-color imaging surveys around field stars, imaging surveys for faint companions to main sequence dwarfs and white dwarfs, surveys of young star clusters and radial velocity monitoring for close companions. Hertzsprung-Russell diagram The main sequence of the Hertzsprung-Russell diagram is the curve where the majority of stars are located in this diagram. ... A white dwarf is an astronomical object which is produced when a low to medium mass star dies. ... Radial velocity is the velocity of an object in the direction of the line of sight. ...


For many years, efforts to discover brown dwarfs were frustrating and searches to find them seemed fruitless. In 1988, however, University of California at Los Angeles professors Eric Becklin and Ben Zuckerman identified a faint companion to GD 165 in an infrared search of white dwarfs. The spectrum of GD 165B was very red and enigmatic, showing none of the features expected of a low-mass red dwarf star. It became clear that GD 165B would need to be classified as a much cooler object than the latest M dwarfs known at that time. GD 165B remained unique for almost a decade until the advent of the Two Micron All Sky Survey (2MASS) when Davy Kirkpatrick, out of the California Institute of Technology, and others discovered many objects with similar colors and spectral features. Year 1988 (MCMLXXXVIII) was a leap year starting on Friday (link displays 1988 Gregorian calendar). ... Berkeley Davis Irvine Los Angeles Merced San Diego Santa Barbara Santa Cruz UC Office of the President in Oakland The University of California (UC) is a public university system in the state of California. ... Flag Seal Nickname: City of Angels Location Location within Los Angeles County in the state of California Coordinates , Government State County California Los Angeles County Mayor Antonio Villaraigosa (D) Geographical characteristics Area     City 1,290. ... Eric E. Becklin received his Ph. ... Red Dwarf is a British science fiction comedy franchise, the primary form of which comprises eight series of a post-watershed television sitcom that ran on BBC2 between 1988 and 1999, and which has achieved a global cult following. ... Observations for the Two Micron All-Sky Survey (2MASS) began in 1997 and were completed in 2001 at two telescopes located one each in the northern and southern hemispheres (Mt. ... The California Institute of Technology (commonly referred to as Caltech)[1] is a private, coeducational research university located in Pasadena, California, in the United States. ...


Today, GD 165B is recognized as the prototype of a class of objects now called "L dwarfs". While the discovery of the coolest dwarf was highly significant at the time it was debated whether GD 165B would be classified as a brown dwarf or simply a very low mass star since observationally it is very difficult to distinguish between the two.


Interestingly, soon after the discovery of GD 165B other brown dwarf candidates were reported. Most failed to live up to their candidacy however, and with further checks for substellar nature, such as the lithium test, many turned out to be stellar objects and not true brown dwarfs. When young (up to a gigayear old), brown dwarfs can have temperatures and luminosities similar to some stars, so other distinguishing characteristics are necessary, such as the presence of lithium. Stars will burn lithium in a little over 100 Myr, at most, while most brown dwarfs will never acquire high enough core temperatures to do so. Thus, the detection of lithium in the atmosphere of a candidate object ensures its status as a brown dwarf. To help compare orders of magnitude of different times this page lists times between 1016 seconds (320 million years) and 1017 seconds (3200 million years). ...


In 1995 the study of brown dwarfs changed dramatically with the discovery of three incontrovertible substellar objects, some of which were identified by the presence of the 6708 Li line. The most notable of these objects was Gliese 229B which was found to have a temperature and luminosity well below the stellar range. Remarkably, its near-infrared spectrum clearly exhibited a methane absorption band at 2 micrometres, a feature that had previously only been observed in gas giant atmospheres and the atmosphere of Saturn's moon, Titan. Methane absorption is not expected at the temperatures of main-sequence stars. This discovery helped to establish yet another spectral class even cooler than L dwarfs known as "T dwarfs" for which Gl 229B is the prototype. Year 1995 (MCMXCV) was a common year starting on Sunday (link will display full 1995 Gregorian calendar). ... General Name, Symbol, Number lithium, Li, 3 Chemical series alkali metals Group, Period, Block 1, 2, s Appearance silvery white/grey Standard atomic weight 6. ... Atmospheric characteristics Atmospheric pressure 140 kPa Hydrogen >93% Helium >5% Methane 0. ... Titan (, from Ancient Greek Τῑτάν) or Saturn VI is the largest moon of Saturn and the only moon known to have a dense atmosphere. ...


Since 1995, when the first brown dwarf was confirmed, hundreds have been identified. Brown dwarfs close to Earth include Epsilon Indi Ba and Bb, a pair of dwarfs around 12 light-years from the Sun. This article is about Earth as a planet. ... Epsilon Indi (ε Ind / ε Indi) is a star approximately 11. ... The Sun (Latin: ) is the star at the center of the Solar System. ...


Theory

The standard mechanism for star birth is through the gravitational collapse of a cold interstellar cloud of gas and dust. As the cloud contracts it heats up. The release of gravitational potential energy is the source of this heat. Early in the process the contracting gas quickly radiates away much of the energy, allowing the collapse to continue. Eventually, the central region becomes sufficiently dense to trap radiation. Consequently, the central temperature and density of the collapsed cloud increases dramatically with time, slowing the contraction, until the conditions are hot and dense enough for thermonuclear reactions to occur in the core of the protostar. For most stars, gas and radiation pressure generated by the thermonuclear fusion reactions within the core of the star will support it against any further gravitational contraction. Hydrostatic equilibrium is reached and the star will spend most of its lifetime burning hydrogen to helium as a main-sequence star. A Protostar is an object that forms by contraction out of the gas of a giant molecular cloud in the interstellar medium. ... In physics, nuclear fusion (a thermonuclear reaction) is a process in which two nuclei join, forming a larger nucleus and releasing energy. ... Hydrostatic equilibrium occurs when compression due to gravity is balanced by a pressure gradient which creates a pressure gradient force in the opposite direction. ...


If, however, the mass of the protostar is less than about 0.08 solar mass, normal hydrogen thermonuclear fusion reactions will not ignite in the core. Gravitational contraction does not heat the small protostar very effectively, and before the temperature in the core can increase enough to trigger fusion, the density reaches the point where electrons become closely packed enough to create quantum electron degeneracy pressure. According to the brown dwarf interior models, typical conditions in the core for density, temperature and pressure are expected to be the following: In physics, nuclear fusion (a thermonuclear reaction) is a process in which two nuclei join, forming a larger nucleus and releasing energy. ... A Protostar is an object that forms by contraction out of the gas of a giant molecular cloud in the interstellar medium. ... The introduction to this article provides insufficient context for those unfamiliar with the subject matter. ...

rho_c sim 10 - 10^3 g/cm^3
P_c sim 10^5 Mbar

Further gravitational contraction is prevented and the result is a "failed star", or brown dwarf that simply cools off by radiating away its internal thermal energy.


Distinguishing high mass brown dwarfs from low mass stars

Lithium: Lithium is generally present in brown dwarfs and not in low-mass stars. Stars, which achieve the high temperature necessary for fusing hydrogen, rapidly deplete their lithium. This occurs by a collision of Lithium-7 and a proton producing two Helium-4 nuclei. The temperature necessary for this reaction is just below the temperature necessary for hydrogen fusion. Convection in low-mass stars ensures that lithium in the whole volume of the star is depleted. Therefore, the presence of the lithium line in a candidate brown dwarf's spectrum is a strong indicator that it is indeed substellar. The use of lithium to distinguish candidate brown dwarfs from low-mass stars is commonly referred to as the lithium test, and was pioneered by Rafael Rebolo and colleagues. General Name, Symbol, Number lithium, Li, 3 Chemical series alkali metals Group, Period, Block 1, 2, s Appearance silvery white/grey Standard atomic weight 6. ... General Name, Symbol, Number Lithium, Li, 3 Series Alkali metal Group, Period, Block 1(IA), 2, s Density, Hardness 535 kg/m3, 0. ... In physics, the proton (Greek proton = first) is a subatomic particle with an electric charge of one positive fundamental unit (1. ... Helium-4 is a non-radioactive and light isotope of helium. ... A spectral line is a dark or bright line in an otherwise uniform and continuous spectrum, resulting from an excess or deficiency of photons in a narrow frequency range, compared with the nearby frequencies. ...

  • However, lithium is also seen in very young stars, which have not yet had a chance to burn it off. Heavier stars like our sun can retain lithium in their outer atmospheres, which never get hot enough for lithium depletion, but those are distinguishable from brown dwarfs by their size.
  • Contrariwise, brown dwarfs at the high end of their mass range can be hot enough to deplete their lithium when they are young. Dwarfs of mass greater than 65 MJ can burn off their lithium by the time they are half a billion years old[Kulkarni], thus this test is not perfect.

Methane: Unlike stars, older brown dwarfs are sometimes cool enough that over very long periods of time their atmospheres can gather observable quantities of methane. Dwarfs confirmed in this fashion include Gliese 229B. Methane is a chemical compound with the molecular formula CH4. ... This page is a candidate for speedy deletion. ...


Luminosity: Main sequence stars cool, but eventually reach a minimum luminosity which they can sustain through steady fusion. This varies from star to star, but is generally at least 0.01% the luminosity of our Sun. Brown dwarfs cool and darken steadily over their lifetimes: sufficiently old brown dwarfs will be too faint to be detectable. This article does not cite any references or sources. ...


Distinguishing low mass brown dwarfs from high mass planets

A remarkable property of brown dwarfs is that they are all roughly the same radius, more or less the radius of Jupiter. At the high end of their mass range (60-90 Jupiter masses), the volume of a brown dwarf is governed primarily by electron degeneracy pressure[citation needed], as it is in white dwarfs; at the low end of the range (1-10 Jupiter masses), their volume is governed primarily by Coulomb pressure, as it is in planets. The net result is that the radii of brown dwarfs vary by only 10-15% over the range of possible masses. This can make distinguishing them from planets difficult. This article or section does not adequately cite its references or sources. ...


In addition, many brown dwarfs undergo no fusion; those at the low end of the mass range (under 13 Jupiter masses) are never hot enough to fuse even deuterium, and even those at the high end of the mass range (over 60 Jupiter masses) cool quickly enough that they no longer undergo fusion after some time on the order of 10 million years. However, there are other ways to distinguish dwarfs from planets:


Density is a clear giveaway. Brown dwarfs are all about the same radius; so anything that size with over 10 Jupiter masses is unlikely to be a planet.


X-ray and infrared spectra are telltale signs. Some brown dwarfs emit X-rays; and all "warm" dwarfs continue to glow tellingly in the red and infrared spectra until they cool to planet like temperatures (under 1000 K). In the NATO phonetic alphabet, X-ray represents the letter X. An X-ray picture (radiograph) taken by Röntgen An X-ray is a form of electromagnetic radiation with a wavelength approximately in the range of 5 pm to 10 nanometers (corresponding to frequencies in the range 30 PHz... Image of two girls in mid-infrared (thermal) light (false-color) Infrared (IR) radiation is electromagnetic radiation of a wavelength longer than that of visible light, but shorter than that of radio waves. ... To help compare different orders of magnitude this page lists temperatures between 1,000 kelvins and 10,000 kelvins. ...


Some astronomers believe that there is in fact no actual black-and-white line separating light brown dwarfs from heavy planets, and that rather there is a continuum. For example, Jupiter and Saturn are both made out of primarily hydrogen and helium, like the Sun. Saturn is nearly as large as Jupiter, despite having only 30% the mass. Three of the giants in our solar system (Jupiter, Saturn, and Neptune) emit more heat than they receive from the Sun. And all four giant planets have their own "planetary systems" -- their moons. In addition, it has been found that both planets and brown dwarfs can have eccentric orbits. Currently, the International Astronomical Union considers objects with masses above the limiting mass for thermonuclear fusion of deuterium (currently calculated to be 13 Jupiter masses for objects of solar metallicity) to be a brown dwarf, whereas those objects under that mass (and orbiting stars or stellar remnants) are considered planets.[2] Logo of the IAU The International Astronomical Union (French: Union astronomique internationale) unites national astronomical societies from around the world. ...


Observations

Image File history File links This is a lossless scalable vector image. ...

Hertzsprung-Russell Diagram
Brown dwarfs

The Hertzsprung-Russell diagram (usually referred to by the abbreviation H-R diagram or HRD, also known as a Colour-Magnitude diagram, or CMD) shows the relationship between absolute magnitude, luminosity, classification, and effective temperature of stars. ... In astronomy, stellar classification is a classification of stars based initially on photospheric temperature and its associated spectral characteristics, and subsequently refined in terms of other characteristics. ... This article or section does not adequately cite its references or sources. ... Red Dwarf is a British science fiction comedy franchise, the primary form of which comprises eight series of a post-watershed television sitcom that ran on BBC2 between 1988 and 1999, and which has achieved a global cult following. ... A subdwarf star, sometimes denoted by sd, is luminosity class VI under the Yerkes spectral classification system. ... Hertzsprung-Russell diagram The main sequence of the Hertzsprung-Russell diagram is the curve where the majority of stars are located in this diagram. ... Hertzsprung-Russell diagram The main sequence of the Hertzsprung-Russell diagram is the curve where the majority of stars are located in this diagram. ... Subgiant are Olly Maw, Dan Hayes and Tushar Joshi, a live dance music band from the UK formed in 2000. ... Giant star is a star that has stopped fusing hydrogen in its core. ... The luminosity class II in the Yerkes spectral classification is given to bright giants. ... Supergiants are the most massive stars. ... This article does not cite its references or sources. ... In astronomy, absolute magnitude is the apparent magnitude, m, an object would have if it were at a standard luminosity distance away from us, in the absence of interstellar extinction. ... In astronomy, absolute magnitude is the apparent magnitude, m, an object would have if it were at a standard luminosity distance away from us, in the absence of interstellar extinction. ... In astronomy, absolute magnitude is the apparent magnitude, m, an object would have if it were at a standard luminosity distance away from us, in the absence of interstellar extinction. ... In astronomy, absolute magnitude is the apparent magnitude, m, an object would have if it were at a standard luminosity distance away from us, in the absence of interstellar extinction. ...

Classification of brown dwarfs

The defining characteristic of spectral class M, the coolest type in the long-standing classical stellar sequence, is an optical spectrum dominated by absorption bands of titanium oxide (TiO) and vanadium oxide (VO) molecules. However, GD 165B, the cool companion to the white dwarf GD 165 had none of the hallmark TiO features of M dwarfs. The subsequent identification of many field counterparts to GD 165B ultimately led Kirkpatrick and others to the definition of a new spectral class, the L dwarfs, defined in the red optical region not by weakening metal-oxide bands (TiO, VO), but strong metal hydride bands (FeH, CrH, MgH, CaH) and prominent alkali lines (Na I, K I, Cs I, Rb I). As of April 2005, over 400 L dwarfs have been identified (see link in references section below), most by wide-field surveys: the Two Micron All Sky Survey (2MASS), the Deep Near Infrared Survey of the Southern Sky (DENIS), and the Sloan Digital Sky Survey (SDSS). In astronomy one method of classifying stars is through the analysis of their absorption spectra, by this method stars are assigned a spectral class. ... General Name, symbol, number titanium, Ti, 22 Chemical series transition metals Group, period, block 4, 4, d Appearance silvery metallic Standard atomic weight 47. ... General Name, symbol, number vanadium, V, 23 Chemical series transition metals Group, period, block 5, 4, d Appearance silver-grey metal Standard atomic weight 50. ... In astronomy one method of classifying stars is through the analysis of their absorption spectra, by this method stars are assigned a spectral class. ... Hydride is the name given to the negative ion of hydrogen, H−. Although this ion does not exist except in extraordinary conditions, the term hydride is widely applied to describe compounds of hydrogen with other elements, particularly those of groups 1–16. ... In chemistry, an alkali (from Arabic: al-qalyالقلوي, القالي ) is a basic, ionic salt of an alkali metal or alkali earth metal element. ... Observations for the Two Micron All-Sky Survey (2MASS) began in 1997 and were completed in 2001 at two telescopes located one each in the northern and southern hemispheres (Mt. ... SDSS Logo The Sloan Digital Sky Survey or SDSS is a major multi-filter imaging and spectroscopic redshift survey using a dedicated 2. ...


As GD 165B is the prototype of the L dwarfs, Gliese 229B is the prototype of a second new spectral class, the T dwarfs. Whereas near-infrared (NIR) spectra of L dwarfs show strong absorption bands of H2O and carbon monoxide (CO), the NIR spectrum of Gliese 229B is dominated by absorption bands from methane (CH4), features that were only found in the giant planets of the solar system and Titan. CH4, H2O, and molecular hydrogen (H2) collision-induced absorption (CIA) give Gliese 229B blue near-infrared colors. Its steeply sloped red optical spectrum also lacks the FeH and CrH bands that characterize L dwarfs and instead is influenced by exceptionally broad absorption features from the alkali metals Na and K. These differences led Kirkpatrick to propose the T spectral class for objects exhibiting H- and K-band CH4 absorption. As of April 2005, 58 T dwarfs are now known. NIR classification schemes for T dwarfs have recently been developed by Adam Burgasser and Tom Geballe. Theory suggests that L dwarfs are a mixture of very low-mass stars and sub-stellar objects (brown dwarfs), whereas the T dwarf class is composed entirely of brown dwarfs. Image of a small dog taken in mid-infrared (thermal) light (false color) Infrared (IR) radiation is electromagnetic radiation of a wavelength longer than visible light, but shorter than microwave radiation. ... Carbon monoxide, with the chemical formula CO, is a colorless, odorless, and tasteless gas. ... Methane is a chemical compound with the molecular formula CH4. ... Titan (, from Ancient Greek Τῑτάν) or Saturn VI is the largest moon of Saturn and the only moon known to have a dense atmosphere. ... General Name, Symbol, Number hydrogen, H, 1 Chemical series nonmetals Group, Period, Block 1, 1, s Appearance colorless Atomic mass 1. ... In chemistry, an alkali (from Arabic: al-qalyالقلوي, القالي ) is a basic, ionic salt of an alkali metal or alkali earth metal element. ...


The majority of flux emitted by L and T dwarfs is in the 1 to 2.5 micrometre near-infrared range. Low and decreasing temperatures through the late M, L, and T dwarf sequence result in a rich near-infrared spectrum containing a wide variety of features, from relatively narrow lines of neutral atomic species to broad molecular bands, all of which have different dependencies on temperature, gravity, and metallicity. Furthermore, these low temperature conditions favor condensation out of the gas state and the formation of grains. In most modern usages of the word spectrum, there is a unifying theme of between extremes at either end. ... The globular cluster M80. ...


Typical atmospheres of known brown dwarfs range in temperature from 2200 down to 750 K (Burrows et al. 2001). Compared to stars, which warm themselves with steady internal fusion, brown dwarfs cool quickly over time; more massive dwarfs cool more slowly than less massive ones. The kelvin (symbol: K) is a unit increment of temperature and is one of the seven SI base units. ...


Observational techniques

Coronographs have recently been used to detect faint objects orbiting bright visible stars, including Gliese 229B.
Sensitive telescopes equipped with charge-coupled devices (CCDs) have been used to search distant star clusters for faint objects, including Teide 1.
Wide-field searches have identified individual faint objects, such as Kelu-1 (30 ly away) An example image from SOHO - NASA A coronagraph is a telescopic attachment designed specifically to block out the harsh, direct light from a star, so that nearby objects can be resolved without burning out the telescopes optics. ...


Milestones

  • 1995: First brown dwarf verified. Teide 1, an M8 object in the Pleiades cluster, is picked out with a CCD in the Spanish Observatory of Roque de los Muchachos of the Instituto de Astrofísica de Canarias.
First methane brown dwarf verified. Gliese 229B is discovered orbiting red dwarf Gliese 229A (20 ly away) using an adaptive optics coronagraph to sharpen images from the 60 inch (1.5 m) reflecting telescope at Palomar Observatory on southern California's Mt. Palomar; followup infrared spectroscopy made with their 200 inch (5 m) Hale telescope shows an abundance of methane.
  • 1998: First X-ray-emitting brown dwarf found. Cha Halpha 1, an M8 object in the Chamaeleon I dark cloud, is determined to be an X-ray source, similar to convective late-type stars.
  • December 15, 1999: First X-ray flare detected from a brown dwarf. A team at the University of California monitoring LP 944-20 (60 Jupiter masses, 16 ly away) via the Chandra X-ray observatory, catches a 2-hour flare.
  • 27 July 2000: First radio emission (in flare and quiescence) detected from a brown dwarf. A team of students at the Very Large Array reported their observations of LP 944-20 in the 15 March 2001 issue of the British journal Nature.

For alternate meanings see Pleiades (disambiguation). ... This article or section does not cite its references or sources. ... The Instituto de Astrofísica de Canarias is an astrophysical research institute based on Tenerife in the Canary Islands, Spain. ... Image of Gliese 229 A and B. Gliese 229 (also written as Gl 229 or GJ 229) is a cool, red dwarf star about 19 light years away in the constellation Lepus. ... A deformable mirror can be used to correct wavefront errors in an astronomical telescope. ... An example image from SOHO - NASA A coronagraph is a telescopic attachment designed specifically to block out the harsh, direct light from a star, so that nearby objects can be resolved without burning out the telescopes optics. ... Palomar Observatory is a privately-owned observatory located in San Diego County, California, 90 miles (145 km) southeast of Mount Wilson Observatory, on Palomar Mountain. ... Palomar Observatory is a privately-owned observatory located in San Diego County, California, 90 miles (145 km) southeast of Mount Wilson Observatory, on Palomar Mountain. ... The Hale Telescope is the largest telescope at the Palomar Observatory. ... This article is about the Hindu moon deity. ... is the 208th day of the year (209th in leap years) in the Gregorian calendar. ... Year 2000 (MM) was a leap year starting on Saturday (link will display full 2000 Gregorian calendar). ... The Very Large Array (VLA) is a radio astronomy observatory located on the Plains of San Augustin, between the towns of Magdalena and Datil, some fifty miles (80 km) west of Socorro, New Mexico, USA. U.S. Route 60 passes through the complex. ... is the 74th day of the year (75th in leap years) in the Gregorian calendar. ... Year 2001 (MMI) was a common year starting on Monday (link displays the 2001 Gregorian calendar). ... Nature is one of the most prominent scientific journals, first published on 4 November 1869. ...

Recent developments

Recent observations of known brown dwarf candidates have revealed a pattern of brightening and dimming of infrared emissions that suggests relatively cool, opaque cloud patterns obscuring a hot interior that is stirred by extreme winds. The weather on such bodies is thought to be extremely violent, comparable to but far exceeding Jupiter's famous storms.


X-ray flares detected from brown dwarfs since late 1999 suggest changing magnetic fields within them, similar to those in very low-mass stars. The name Magnetic Fields has been used by: A 1981 album by Jean Michel Jarre; see Magnetic Fields (album) (Les Chants Magnetiques) A computer game developer; see Magnetic Fields (computer game developer) The Magnetic Fields, a band led by Stephin Merritt For magnetic fields in general, see magnetic field. ...


A brown dwarf Cha 110913-773444 located 500 light years away in the constellation Chamaeleon may be in the process of forming a mini solar system. Astronomers from Pennsylvania State University have detected what they believe to be a disk of gas and dust similar to the one hypothesized to have formed our own solar system. Cha 110913-773444 is the smallest brown dwarf found to date (8 Jupiter masses) and if it formed a solar system it would be the smallest known object to have one. Their findings will be published in the Dec. 10 issue of the Astrophysical Journal Letters The Pennsylvania State University (commonly known as Penn State) is a state-related, land-grant university. ... Cha 110913-773444 (Cha 110913 for short) is an astronomical object surrounded by what appears to be a protoplanetary disk. ...


Some notable brown dwarfs

  • 2M1207 - first brown dwarf discovered with a planetary mass in orbit about it
  • WD0137-349 B - first confirmed brown dwarf to have survived the primary's red giant phase (Maxted et al. 2006, Nature, 442, 543).
  • It has also been predicted, by some Astronomers, that the Sun (Sol) may be orbited by an, as yet unobserved, brown dwarf (sometimes referred to as Nemesis) which interacts with the Oort cloud (and may have helped shape the position of the dwarf planets) [3].
Table of Firsts
Brown Dwarfs
Title Brown Dwarf Name Spectral Type RA/Dec Constellation Notes
First discovered Gliese 229 B T6.5 06h10m34.62s -21°51'52.1" Lepus Discovered 1995
First directly imaged Gliese 229 B T6.5 06h10m34.62s -21°51'52.1" Lepus Discovered 1995
First verified Teide 1 M8 3h47m18.0s +24°22'31" Taurus 1995
First with planemo 2MASSW J1207334-393254 M8 12h07m33.47s -39°32'54.0" Centaurus
First with a dust disk
First with bipolar outflow
First field type (solitary) Teide 1 M8 3h47m18.0s +24°22'31" Taurus 1995
First as a companion to a normal star Gliese 229 B T6.5 06h10m34.62s -21°51'52.1" Lepus 1995
First as a companion to a white dwarf
First as a companion to a neutron star
First in a multi-star system
First binary brown dwarf Epsilon Indi Ba, Bb [1] T1 + T6 Indus Distance: 3.626pc
First trinary brown dwarf DENIS-P J020529.0-115925 A/B/C L5, L8 and T0 02h05m29.40s -11°59'29.7" Cetus Delfosse et al 1997, [mentions]
First halo brown dwarf 2MASS J05325346+8246465 sdL7 05h32m53.46s +82°46'46.5" Gemini Adam J. Burgasser, et al. 2003
First Late-M spectra Teide 1 M8 3h47m18.0s +24°22'31" Taurus 1995
First L spectra
First T spectra Gliese 229 B T6.5 06h10m34.62s -21°51'52.1" Lepus 1995
Latest T spectrum ULAS J0034-00 T8.5 Cetus 2007
First mistaken as a planet
First X-ray-emitting Cha Halpha 1 M8 Chamaeleon 1998
First X-ray flare LP 944-20 M9V 03h39m35.22s -35°25'44.1" Fornax 1999
First radio emission (in flare and quiescence) LP 944-20 M9V 03h39m35.22s -35°25'44.1" Fornax 2000
Table of Extremes
Brown Dwarfs
Title Brown Dwarf Name Spectral Type RA/Dec Constellation Notes
Oldest
Youngest
Heaviest
Metal-rich
Metal-poor 2MASS J05325346+8246465 sdL7 05h32m53.46s +82°46'46.5" Gemini distance is ~10-30pc, metallicity is 0.1-0.01ZSol
Lightest
Largest
Smallest Cha 110913-773444 L 11h09m13.63s -77°34'44.6"

Chamaeleon Image File history File links Splitsection. ... 2M1207, 2M1207A or 2MASSW J1207334-393254 is a brown dwarf star located in the constellation Hydra; a companion object, 2M1207b, is believed to be one of the first extrasolar planets to be directly imaged, and is the first exoplanet to be discovered in orbit of a brown dwarf. ... According to the Hertzsprung-Russell diagram, a red giant is a large non-main sequence star of stellar classification K or M; so-named because of the reddish appearance of the cooler giant stars. ... Standards Of Learning SOL stands for The Standards Of Learning. ... Nemesis is a hypothetical red dwarf star or brown dwarf, orbiting the Sun at a distance of about 50,000 to 100,000 AU, somewhat beyond the Oort cloud. ... This image is an artists rendering of the Oort cloud and the Kuiper Belt. ... Artists impression of Pluto (background) and its satellite Charon (foreground). ... Image of Gliese 229 A and B. Gliese 229 (also written as Gl 229 or GJ 229) is a cool, red dwarf star about 19 light years away in the constellation Lepus. ... Lepus (IPA: , Latin: ) is a constellation, lying just south of the Celestial equator, below the constellation Orion, and possibly representing a hare being chased by Orion the hunter. ... Lepus (IPA: , Latin: ) is a constellation, lying just south of the Celestial equator, below the constellation Orion, and possibly representing a hare being chased by Orion the hunter. ... Taurus (IPA: , Latin: , symbol , ) is one of the constellations of the zodiac. ... This article is being considered for deletion in accordance with Wikipedias deletion policy. ... 2M1207, 2M1207A or 2MASSW J1207334-393254 is a brown dwarf star located in the constellation Hydra; a companion object, 2M1207b, is believed to be one of the first extrasolar planets to be directly imaged, and is the first exoplanet to be discovered in orbit of a brown dwarf. ... Centaurus (Latin for centaur) was one of the 48 constellations listed by Ptolemy, and counts also among the 88 modern constellations. ... A protoplanetary disc (also protoplanetary disk, proplyd) is an accretion disc surrounding a T Tauri star. ... The Boomerang Nebula is an excellent example of a bipolar outflow. ... This article or section does not adequately cite its references or sources. ... For the Hugo Award-winning story by Larry Niven, see Neutron Star (story). ... Epsilon Indi (ε Ind / ε Indi) is a star approximately 11. ... Cetus (a name from Greek mythology, referring to a Whale or Sea monster, see Ceto) is a constellation of the southern sky, in the region known as the Water, near other watery constellations like Aquarius, Pisces, and Eridanus. ... 2MASS 0532+8246 (full designation 2MASS J05325346+8246465) is possibly the first halo brown dwarf and the first substellar subdwarf. ... A subdwarf star, sometimes denoted by sd, is luminosity class VI under the Yerkes spectral classification system. ... Gemini (IPA: , Latin: , symbol , ) is one of the constellations of the zodiac known as the twins. It is part of the winter sky, lying between Taurus to the west and the dim Cancer to the east, with Auriga and the near-invisible Lynx to the north and Monoceros and Canis... The eight planets and three dwarf planets of the Solar System. ... For other uses of the word, see chameleon (disambiguation) Chamaeleon (Latin for chameleon) is a minor southern constellation. ... Fornax (Latin for furnace) is a southern constellation which was first introduced by Nicolas Louis de Lacaille under the name Fornax Chemica (Latin for chemical furnace). ... 2MASS 0532+8246 (full designation 2MASS J05325346+8246465) is possibly the first halo brown dwarf and the first substellar subdwarf. ... A subdwarf star, sometimes denoted by sd, is luminosity class VI under the Yerkes spectral classification system. ... Gemini (IPA: , Latin: , symbol , ) is one of the constellations of the zodiac known as the twins. It is part of the winter sky, lying between Taurus to the west and the dim Cancer to the east, with Auriga and the near-invisible Lynx to the north and Monoceros and Canis... Metallicity is a number denoting the mass fraction of a star which consists of metals. ... The Sun (Latin: ) is the star at the center of the Solar System. ... Cha 110913-773444 (Cha 110913 for short) is an astronomical object surrounded by what appears to be a protoplanetary disk. ... For other uses of the word, see chameleon (disambiguation) Chamaeleon (Latin for chameleon) is a minor southern constellation. ...

Distance: 163ly (50pc), 1.8 RJupiter
Furthest to primary star
Nearest to primary star
Furthest
Nearest Epsilon Indi Ba, Bb [2] T1 + T6 Indus Distance: 3.626pc
Nearest binary Epsilon Indi Ba, Bb [3] T1 + T6 Indus Distance: 3.626pc
Brightest
Dimmest
Hottest
Coolest ULAS J0034-00 T8.5 Cetus ~50ly, Gemini Observatory
Most dense
Least dense

Remote Authentication Dial In User Service (RADIUS) is an AAA (authentication, authorization and accounting) protocol for applications such as network access or IP mobility. ... Adjectives: Jovian Atmosphere [4] Surface pressure: 20–200 kPa[9] (cloud layer) Scale height: 27 km Composition: Jupiter (IPA: or ) is the fifth planet from the Sun and the largest planet within the solar system. ... Epsilon Indi (ε Ind / ε Indi) is a star approximately 11. ... Epsilon Indi (ε Ind / ε Indi) is a star approximately 11. ...

Brown dwarfs in fiction

  • A brown dwarf is the setting of the nearest router on the galactic Internet in Accelerando
  • Brown dwarf stars feature prominently in Karl Schroeder's novel Permanence.

Accelerando (ISBN 0441012841) is a 2005 science fiction novel by British author Charles Stross. ... Karl Schroeder (born September 4, 1962) is a Canadian author. ...

See also

Look up Brown dwarf in
Wiktionary, the free dictionary.
Wikimedia Commons has media related to:

Wikipedia does not have an article with this exact name. ... Wiktionary (a portmanteau of wiki and dictionary) is a multilingual, Web-based project to create a free content dictionary, available in over 150 languages. ... Image File history File links Commons-logo. ... STAR is an acronym for: Organizations Society of Ticket Agents and Retailers], the self-regulatory body for the entertainment ticket industry in the UK. Society for Telescopy, Astronomy, and Radio, a non-profit New Jersey astronomy club. ... Orange dwarfs are main sequence stars of spectral type K. Categories: Star stubs | Orange dwarfs ... Red Dwarf is a British science fiction comedy franchise, the primary form of which comprises eight series of a post-watershed television sitcom that ran on BBC2 between 1988 and 1999, and which has achieved a global cult following. ... Large solar flare recorded by SOHO EIT304 instrument in the ultraviolet. ... A black dwarf is a hypothetical astronomical object: a white dwarf so old that it has cooled down so that it no longer emits significant heat or light. ... The terms Dark Star or Darkstar may refer to: Dark star, a theoretical star whose gravity is strong enough to trap light, mostly superseded by the concept of black holes. RQ-3 Dark Star, a military drone developed by the United States Dark Star (band), an English rock band Dark... An extrasolar planet, or exoplanet, is a planet beyond the Solar System. ... Planetars are used in astronomy to represent one of two concepts: Planetars are brown dwarfs which formed through accretion or core collapse within a circumstellar disc, forming like a planet does. ... Sub-brown dwarfs or brown sub-dwarfs are cold masses smaller than the low-mass cut-off for brown dwarfs. ... This article or section does not adequately cite its references or sources. ... The first free-floating brown dwarf discovered is Teide 1 in 1995. ... In astrophysics and cosmology, dark matter refers to hypothetical matter of unknown composition that does not emit or reflect enough electromagnetic radiation to be observed directly, but whose presence can be inferred from gravitational effects on visible matter. ...

References

  1. ^ Boss, Alan (2001-04-03). Are They Planets or What? (English). Carnegie Institution of Washington. Retrieved on 2006-06-08.
  2. ^ Working Group on Extrasolar Planets: Definition of a "Planet". IAU position statement (February 28, 2003). Retrieved on 2006-09-09.
  3. ^ Daniel P. Whitmire, Albert A. Jackson. 1984, Nature, 308, 713. Also Richard A. Muller. 2004, Geological Society of America Special Paper 356, 659-665]

Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 159th day of the year (160th in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 252nd day of the year (253rd in leap years) in the Gregorian calendar. ...

External links

History

  • S. S. Kumar, Low-Luminosity Stars. Gordon and Breach, London, 1969—an early overview paper on brown dwarfs
  • The Columbia Encyclopedia

Details

The Space Telescope Science Institute (STScI) is an organization founded by NASA to manage and direct research done with the Hubble Space Telescope. ... According to the Hertzsprung-Russell diagram, a red dwarf star is a small and relatively cool star, of the main sequence, either late K or M spectral type. ... This brown dwarf (smaller object) orbits the star Gliese 229, which is located in the constellation Lepus about 19 light years from Earth. ...

Stars


  Results from FactBites:
 
brown dwarf (1232 words)
By this criterion, brown dwarfs are held to form in the same way as stars, as condensations in an interstellar gas cloud (see stars, evolution).
The more massive a brown dwarf, the higher its surface temperature, though a typical value is about 1000 K. The first brown dwarf to be confirmed, in 1995, on the basis of a combination of mass determination, spectroscopic studies, and direct imaging was Gliese 229B.
At the high-mass, high-temperature end of the brown dwarf scale are the ultra-cool dwarfs, with dusty atmospheres and a spectral type of M7 or later.
  More results at FactBites »

 
 

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